crush: fix has_v4_buckets()

crush: fix has_v4_buckets()

alg, not type!

This bug made us incorrectly think we were using v4 features when user type
5 was being used.  That's currently 'rack' with recent crush maps, but
was other types for clusters that were created with older versions.  This
is clearly problematic as it will lock out non-hammer clients incorrectly,
breaking deployments on upgrade.

Fixes: #11364
Backport: hammer
Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 38b35ab9d17eb84ac178c4cd3ebcf2ec0f66d8b6)